engleski

Water hardness shows strong impact on the photodynamic activity of cationic pyridylporphyrins against Legionella pneumophila and biofilm

Legionella pneumophila, a gram negative, aerobic bacterium, is a member of the opportunistic premises plumbing pathogens (OPPP) group. The main characteristics of this group of pathogens are their capacity to live in different aquatic systems, the possibility of biofilm formation and their resistance to common disinfection methods , such as chlorination and high temperatures1. To date, only a small number of studies of photodynamic inactivation (PDI) of Legionella pneumophila have been published. Our research group recently described PDI with cationic tetrapyrid-3-ylporphyrin and two cationic tripyrid-3-ylporphyrins, one hydrophilic and the other conjugated with long alkyl chain (C18), on L. pneumophila. Although all tested porphyrins showed a strong PDI effect on L. pneumophila, the amphiphilic tricationic porphyrin with a long chain stood out with its strong anti-legionella activity already at nanomolar concentration (25 nM)2. In this work, we study the effect of water samples of different hardness, taken from water wells, on the same porphyrins and the PDI of L. pneumophila (Philadelphia strain). The source of irradiation is a LED based violet and blue light (395 nm with fluence rate 20 mW/cm2 for microbiology experiments, and 411 nm with 3.5- 11 mW/cm2 fluence rate for studies of photophysical properties, respectively). In the case of tested porphyrins, their stability, spectroscopic properties as well as singlet oxygen production by photodegradation of water soluble 9, 10-anthracenediyl- bis(methylene)dimalonic acid (ABMDMA) will be described, while the effect on L. pneumophila will be investigated through MEK determination, photoinactivation tests and the destruction tests of the early and late biofilms. We will discuss the observed strong impact of water hardness on the PDI of L. pneumophila Philadelphia-1 and biofilm formation and growth.

Porphyrins ; Photodynamic inactivation ; Legionella pneumophila ; Biofilm ; Singlet oxygen

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